Contained modes in mirrors with sheared rotation

Abstract

In mirrors with E × B rotation, a fixed azimuthal perturbation in the lab frame can appear as a wave in the rotating frame. If the rotation frequency varies with radius, the plasma-frame wave frequency will also vary radially due to the Doppler shift. A wave that propagates in the high rotation plasma region might therefore be evanescent at the plasma edge. This can lead to radially localized Alfven eigenmodes with high azimuthal mode numbers. Contained Alfven modes are found both for peaked and non-peaked rotation profiles. These modes might be useful for alpha channeling or ion heating, as the high azimuthal wave number allows the plasma wave frequency in the rotating frame to exceed the ion cyclotron frequency.

Isorotation and differential rotation in a magnetic mirror with imposed E×B rotation

“…14 The perturbations created by the differential rotation may be increasing the heating efficiency of the capacitor bank, by launching contained Alfvén waves that propagate from the mirror side and get absorbed in the midplane. The theory of this heating effect for rotating plasma configurations has been studied by Fetterman and Fisch, 24 and is the subject of ongoing research.…”

The alpha channeling effect

“…The proportion of energy channeled to the potential depends on the wave characteristics. Like in a simple mirror, waves can be set up in a centrifugally rotating mirror plasma that eject α-particles while capturing their energy in the wave fields [73,74]. However, waves with low frequency, which includes a fixed azimuthal perturbation (zero frequency), can be used instead to support the radial potential [75].…”

Pushing Particles with Waves: Current Drive and <i>α</i>-Channeling

“…In a generalization of the channeling effect in rotating plasma, depending on the wave characteristics, some of the α-particle energy can be channeled to electric potential energy and some channeled to the wave energy [98]. Waves can be arranged that eject α-particles while capturing their energy in the wave fields [99,100]. A fixed azimuthal perturbation can also be used to capture α-particle energy to support the radial potential [101], replacing the need for setting up the potential through endplate electrodes.…”